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(#) Creating an Animatable during composition without using `remember`

!!! ERROR: Creating an Animatable during composition without using `remember`
   This is an error.

Id
:   `UnrememberedAnimatable`
Summary
:   Creating an Animatable during composition without using `remember`
Severity
:   Error
Category
:   Correctness
Platform
:   Any
Vendor
:   Jetpack Compose
Identifier
:   androidx.compose.animation.core
Feedback
:   https://issuetracker.google.com/issues/new?component=612128
Min
:   Lint 8.0 and 8.1
Compiled
:   Lint 8.7+
Artifact
:   [androidx.compose.animation:animation-core-android](androidx_compose_animation_animation-core-android.md.html)
Since
:   1.5.0
Affects
:   Kotlin and Java files and test sources
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/animation/animation-core-lint/src/main/java/androidx/compose/animation/core/lint/UnrememberedAnimatableDetector.kt)
Tests
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/animation/animation-core-lint/src/test/java/androidx/compose/animation/core/lint/UnrememberedAnimatableDetectorTest.kt)
Copyright Year
:   2021

Animatable instances created during composition need to be `remember`ed,
otherwise they will be recreated during recomposition, and lose their
state. Either hoist the Animatable to an object that is not created
during composition, or wrap the Animatable in a call to `remember`.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/test/{.kt:12:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:13:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:15:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
src/test/{.kt:20:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:21:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:23:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
src/test/{.kt:28:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:29:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:31:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
src/test/{.kt:41:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:42:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:44:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
src/test/{.kt:48:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:49:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:51:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
src/test/{.kt:58:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:59:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:61:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
src/test/{.kt:66:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:67:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:69:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
src/test/{.kt:77:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable = Animatable&lt;Boolean, Any&gt;(false)
                     ----------
src/test/{.kt:78:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable2 = Animatable(0f)
                      ----------
src/test/{.kt:80:Error: Creating an Animatable during composition
without using remember [UnrememberedAnimatable]
    val animatable3 = Animatable(Color.Red)
                      ----------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/test/{.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package test

import androidx.compose.animation.*
import androidx.compose.animation.core.*
import androidx.compose.runtime.*
import androidx.compose.ui.graphics.*

@Composable
fun Test() {
    // Float function and constructor from androidx.compose.animation.core
    val animatable = Animatable<Boolean, Any>(false)
    val animatable2 = Animatable(0f)
    // Color function from androidx.compose.animation
    val animatable3 = Animatable(Color.Red)
}

val lambda = @Composable {
    // Float function and constructor from androidx.compose.animation.core
    val animatable = Animatable<Boolean, Any>(false)
    val animatable2 = Animatable(0f)
    // Color function from androidx.compose.animation
    val animatable3 = Animatable(Color.Red)
}

val lambda2: @Composable () -> Unit = {
    // Float function and constructor from androidx.compose.animation.core
    val animatable = Animatable<Boolean, Any>(false)
    val animatable2 = Animatable(0f)
    // Color function from androidx.compose.animation
    val animatable3 = Animatable(Color.Red)
}

@Composable
fun LambdaParameter(content: @Composable () -> Unit) {}

@Composable
fun Test2() {
    LambdaParameter(content = {
        // Float function and constructor from androidx.compose.animation.core
        val animatable = Animatable<Boolean, Any>(false)
        val animatable2 = Animatable(0f)
        // Color function from androidx.compose.animation
        val animatable3 = Animatable(Color.Red)
    })
    LambdaParameter {
        // Float function and constructor from androidx.compose.animation.core
        val animatable = Animatable<Boolean, Any>(false)
        val animatable2 = Animatable(0f)
        // Color function from androidx.compose.animation
        val animatable3 = Animatable(Color.Red)
    }
}

fun test3() {
    val localLambda1 = @Composable {
        // Float function and constructor from androidx.compose.animation.core
        val animatable = Animatable<Boolean, Any>(false)
        val animatable2 = Animatable(0f)
        // Color function from androidx.compose.animation
        val animatable3 = Animatable(Color.Red)
    }

    val localLambda2: @Composable () -> Unit = {
        // Float function and constructor from androidx.compose.animation.core
        val animatable = Animatable<Boolean, Any>(false)
        val animatable2 = Animatable(0f)
        // Color function from androidx.compose.animation
        val animatable3 = Animatable(Color.Red)
    }
}

@Composable
fun Test4() {
    val localObject = object {
        // Float function and constructor from androidx.compose.animation.core
        val animatable = Animatable<Boolean, Any>(false)
        val animatable2 = Animatable(0f)
        // Color function from androidx.compose.animation
        val animatable3 = Animatable(Color.Red)
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/animation/animation-core-lint/src/test/java/androidx/compose/animation/core/lint/UnrememberedAnimatableDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `UnrememberedAnimatableDetector.notRemembered`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=612128.

(##) Including

!!!
   This is not a built-in check. To include it, add the below dependency
   to your project.

```
// build.gradle.kts
implementation("androidx.compose.animation:animation-core-android:1.8.0-alpha07")

// build.gradle
implementation 'androidx.compose.animation:animation-core-android:1.8.0-alpha07'

// build.gradle.kts with version catalogs:
implementation(libs.animation.core.android)

# libs.versions.toml
[versions]
animation-core-android = "1.8.0-alpha07"
[libraries]
# For clarity and text wrapping purposes the following declaration is
# shown split up across lines, but in TOML it needs to be on a single
# line (see https://github.com/toml-lang/toml/issues/516) so adjust
# when pasting into libs.versions.toml:
animation-core-android = {
    module = "androidx.compose.animation:animation-core-android",
    version.ref = "animation-core-android"
}
```

1.8.0-alpha07 is the version this documentation was generated from;
there may be newer versions available.

NOTE: These lint checks are **also** made available separate from the main library.
You can also use `androidx.compose.animation:animation-core-lint:1.8.0-alpha07`.


[Additional details about androidx.compose.animation:animation-core-android](androidx_compose_animation_animation-core-android.md.html).
(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("UnrememberedAnimatable")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("UnrememberedAnimatable")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection UnrememberedAnimatable
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="UnrememberedAnimatable" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'UnrememberedAnimatable'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore UnrememberedAnimatable ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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